1. Field of the Invention
This invention broadly relates to a method and apparatus for covering cargo such as cargo carried by a truck, trailer, railway car or other vehicle. More specifically, this invention concerns a method and apparatus for covering cargo with a tarp by use of a frame that is releasably connected to the tarp.
2. Description of the Related Art
Trucks, trailers and railway cars have long served the important function of moving consumer, commercial and industrial goods and equipment from one location to another. Cargo that is moved over relatively short distances or that is not likely to be degraded by the effects of weather is sometimes left uncovered. However, cargo that is moved over longer distances and/or left outdoors for significant lengths of time is frequently covered or otherwise protected to guard against the possibility of rain, snow, dust, dirt and the like from adversely affecting the cargo.
Many trucks, trailers, railway cars and other vehicles for carrying cargo have a permanently enclosed structure that includes rigid sidewalls and a roof that cover the vehicle's floor or bed. For example, railway boxcars commonly have steel walls and a roof, and are often used to carry pallet-sized units of cargo or palletized assemblies of smaller cargo that can be loaded by a forklift through doors provided in one or more of the walls. Many semi-trailers and larger trucks also have a permanently enclosed structure, with a door or a pair of doors at the rear end of the bed to provide access to the interior space.
Trucks, trailers and railway cars with flat beds are also widely used to haul a variety of loads. Flat bed vehicles are particularly advantageous for carrying larger cargo since there are typically no permanent walls or other structure extending upwardly from the bed that might otherwise impede access to the bed and hinder loading or unloading the cargo. For example, relatively large construction materials such as long steel or concrete beams, culverts and pipes can be readily loaded onto a flat bed vehicle by using a forklift and approaching the vehicle from its side. Such materials are often difficult if not impossible to load onto vehicles having permanently enclosed structures because the length of the materials frequently exceeds the width of the doors.
However, in order to protect cargo on flat bed vehicles from dust, dirt, snow, rain and other elements, it is often desirable to cover the cargo with a tarp once the cargo has been placed on the bed. Such tarps are commonly made of a canvas fabric since the strength of the canvas fabric can safely withstand the effects of wind during high speed movement of the vehicle. In some instances, a plastic underlayment tarp is placed beneath the canvas tarp to provide an additional barrier to guard against moisture from reaching the cargo.
One conventional method of covering flat bed cargo with a tarp involves placing a folded tarp atop a portion of the cargo and then unfolding the tarp while walking across the top of the cargo. Once unfolded, a cord such as a rope, or a series of cords such as rope segments or elastic straps, is used to tie a peripheral edge portion of the tarp to the bed at a number of locations spaced along the perimeter of the bed. For example, the tarp may have a plurality of grommets along its edges and rope segments or elastic straps may be secured to each grommet and a respective eyelet or other anchoring structure located along the periphery of the bed in order to bind the tarp to the vehicle.
However, canvas tarps are often heavy and difficult to maneuver to a position properly aligned with the cargo and the bed. Moreover, the practice of walking along the top of the load can present significant hazards and lead to serious injury. For example, cargo that includes large round pipes or other curved surfaces may not have adequate horizontal surfaces to provide safe footing. As another example, the cargo may be slippery due to rain or snow. If a plastic underlayment tarp is used, the plastic material can significantly increase the risk of serious injury, especially if the plastic material is smooth or slippery.
Occasionally, a forklift is used to lift the folded tarp to the top of the load in order to ease the task of moving the heavy tarp. Unfortunately, such a procedure does not ease the burden or lessen the risks associated with the remaining tasks of unfolding the tarp and aligning the tarp to the bed and the cargo. Unfolding and maneuvering the tarp while walking across the top of the cargo is often practiced because the height of the cargo precludes unfolding the tarp from the ground. Moreover, there is often insufficient space between the edge of the bed and the cargo to safely walk while unfolding the tarp.
Efforts have been undertaken in the past to facilitate covering loads on flat bed vehicles. For example, U.S. Pat. No. 5,007,672 describes a cover system that includes a plurality of inverted, U-shaped bows that fit into side posts which, in turn, are received in brackets next to the bed; tarp sections including side sections and a top section are placed over the posts and to the bows. However, the bows and posts represent an additional expense as well as additional weight, and the problem of unfolding the tarp across the top of the bows is presented.
U.S. Pat. Nos. 5,338,084 and 5,152,575 describe cover systems for flat bed vehicles wherein a series of inverted bows secured to the vehicle are movable in a path along the length of the bed, and wherein a tarp connected to the bows unfolds in accordion-like fashion as the bows are moved to respective locations along the bed. However, the bows as well as structure provided to guide movement of the bows represents a significant additional expense as well as additional weight that may adversely affect fuel economy. An additional expense may be encountered in customizing the tarp to fit and connect with the bows. Furthermore, the bows may interfere with access to cargo even after the bows are moved forwardly to uncover the load, especially if the cargo is located near the front of the bed.